1. Field of the Invention
The present invention relates to a light emitting device.
2. Description of the Related Art
In recent years, a large number of light emitting devices have been developed, that use of a light emitting element such as a light emitting diode (hereinafter sometimes called the “LED”) as a light source. Some of these light emitting devices are provided with a reflector around a LED to improve the utilization efficiency of light emitted from the LED. JP-2004-327632-A discloses a light emitting device which includes a light emitting element mounted on a mount portion defined at the center of the top surface of a package. The package comprises a base having the mount portion, and a frame. A lower end of an inner peripheral surface of the frame is bonded to a side surface of the base over its entirety. An overhang is formed around a portion of the inner surface of the frame above which protrudes beyond the base. The overhang projects toward the mount portion, and the bottom surface of the overhang is not in contact with the base. Then, JP-2004-327632-A describes that the inner peripheral surface of the overhang is inclined such that the diameter of the opening becomes larger toward the top of the package, and the arithmetical average roughness of the inner peripheral surface is reduced to 0.01 [μm] or less, whereby light emitted horizontally from the light emitting element can be reflected upward on the inner peripheral surface and can be efficiently radiated from the package to the outside.
More specifically, JP-2004-327632-A describers a light emitting device which comprises a reflector arranged on a base, and a LED placed inside the reflector. In a light emitting device having such a basic structure, an interstice is formed for a variety of reasons between the bottom of the reflector and the surface on which the bottom is carried. For example, JP-2004-327632-A describes that an interstice is intentionally formed between the surface of a base and the bottom of a reflector (frame) in order to avoid a crack from occurring in a joint of the surface of the base with the bottom of the reflector due to a stress which is generated due to the difference in coefficient of thermal expansion between the base and reflector (frame). Also, an interstice can be unintentionally formed between the bottom of the reflector and a surface on which the bottom is carried. For example, when a base has a surface which presents a low flatness, or when a base warps for some reason, an interstice is formed between the surface of the base and the bottom of the reflector. Also, an insulating layer, a wiring layer and the like may be disposed on the surface of a base, and a reflector may be disposed on these layers. In this event, when the insulating layer and/or wiring layer are uneven, an interstice is formed between the insulating layer and wiring layer and the reflector.
Anyway, if an interstice exists between the bottom of the reflector and the surface on which the bottom is carried, part of light emitted from the light emitting element will be introduced into the interstice, resulting in a lower light utilization efficiency.
JP-2004-327632-A describes that the light emitted horizontally from the light emitting element can be prevented from being introduced into the interstice between the base and frame by the protrusion formed on the lower surface of the overhang. JP-2004-327632-A also describes that the light prevented from being introduced into the interstice between the base and frame by the protrusion is efficiently reflected on the inner peripheral surface of the overhang.